The health ministry said all 321 people infected are co-workers of the first patient, who was diagnosed at a hospital two days ago and was from the densely populated Western province.
The cluster in the suburbs of Sri Lanka’s capital Colombo was identified despite the government saying it has successfully controlled the spreading of the virus.
Trying to contain the spread of the virus, the government imposed a curfew in two suburbs where the majority of patients live, closed schools and universities, and imposed restrictions on public transport.
For more than two months, Sri Lanka health officials have been saying that they have prevented a community spread of the virus and that the patients being reported belonged to two known clusters.
The country has reported 3,471 patients with 13 deaths.
Of the total patients, 3,259 have recovered.
